锂离子电池活性材料硅酸亚铁锂的制备及性能研究-物理化学专业论文.docxVIP

万方数据 万方数据 摘要 关键词：锂离子电池，电化学，Li2FeSiO4，石墨烯，溶胶凝胶 II Abst Abstract Abstract Lithium-ion battery has been used widely in portable electronics because of the advantages of high energy density and environmentally friendliness. However, the most key factor limiting the further improvment of energy density is the lower capacity of anode materials, so the researches on anode materials become a hotpot. Nowadays a new material named Li2FeSiO4 have drawn researchers’ attention due to its low cost, environmental friendly and high theoretical capacity. Hower, its conductivity is low. In this work, we prepared the composites of Li2FeSiO4 and different carbon used different SiO2 with different morphology as raw materials, and research on its preparation process and electrochemical performance. The main content in this paper are as follows: Li2FeSiO4/C and Li2-xFeSi1-xPxO4/C was successfully obtained using spherical nano-SiO2 as raw materials. The results show that there is impurity Fe2O3 in Li2FeSiO4/C, while Li2-xFeSi1-xPxO4/C shows different structure and performance, among which there is no impurity in the product when x=3%. And the discharge capacity of Li1.97FeSi0.97P0.03O4/C can reach 179 mAh g-1 at the electric current density of 10mA g-1, corresponding to more than one lithium insertion per formula unit. The discharge capacities 3LFS after five cycles were reduced by approximately 8.9%. After five cycles, the specific discharge capacitity reach stable. The discharge capacity retentions after 30 cycles is approximately 94.5% of the corresponding discharge capacities in the sixth cycle. In addition, through exploration it can be fould that there is an autocatalysis process in the reaction, the H2 produced by NH4H2PO4 can improve the reducibility of the system, which preventing the appearance of impurity containing Fe3+. Li1.97FeSi0.97P0.03O4/C/G combining two kinds of carbon (G=Graphene) was successfully obtained. In these experiments the amounts of amorphous car